WO2019086236A1 - Termination unit - Google Patents
Termination unit Download PDFInfo
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- WO2019086236A1 WO2019086236A1 PCT/EP2018/078124 EP2018078124W WO2019086236A1 WO 2019086236 A1 WO2019086236 A1 WO 2019086236A1 EP 2018078124 W EP2018078124 W EP 2018078124W WO 2019086236 A1 WO2019086236 A1 WO 2019086236A1
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- WIPO (PCT)
- Prior art keywords
- current
- electrical steel
- termination unit
- shielding
- component
- Prior art date
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Classifications
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
- C23C14/34—Sputtering
- C23C14/3407—Cathode assembly for sputtering apparatus, e.g. Target
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
- C23C14/34—Sputtering
- C23C14/35—Sputtering by application of a magnetic field, e.g. magnetron sputtering
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/32—Gas-filled discharge tubes
- H01J37/34—Gas-filled discharge tubes operating with cathodic sputtering
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/32—Gas-filled discharge tubes
- H01J37/34—Gas-filled discharge tubes operating with cathodic sputtering
- H01J37/3411—Constructional aspects of the reactor
- H01J37/3435—Target holders (includes backing plates and endblocks)
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K11/00—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection
- H02K11/01—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection for shielding from electromagnetic fields, i.e. structural association with shields
- H02K11/014—Shields associated with stationary parts, e.g. stator cores
Definitions
- the present invention relates to a termination unit for a deposition system. More specifically it relates to a termination unit which is adapted for transferring power to the target it is carrying while being in operation.
- a plasma is generated in a low pressure chamber in which an inert gas such as Argon, or an active gas such as oxygen or nitrogen is present, and a high voltage is applied between a so called “sputter target" (containing the material to be deposited) and a "substrate” upon which a layer of the sputter material is to be deposited.
- the Argon atoms are ionized, and the sputter target is bombarded by the Argon ions, so that atoms are freed from the sputter target, and move to the substrate, where they are deposited.
- three kinds of sputter targets are being used: planar circular disk targets, planar rectangular targets, and rotational cylindrical targets.
- DC power typically used when the deposited layer is less conductive and RF is typically used when the target material is quite insulating.
- AC or pulsed power e.g. at a frequency of 1 to 100 kHz
- RF power e.g. at a frequency of 0.3 to 100 MHz
- the main function of a termination unit in prior art deposition systems is to carry the target and potentially also to rotate the target.
- the termination unit may for example be a PVD source termination unit. Since PVD deposition is done with a gas at low pressure, the termination unit has to be vacuum tight, also during a possible rotation of the target. PVD deposition refers to a physical vapor phase deposition technique whereby material from a consumption target is deposited on a substrate on which a thin layer is desired to be applied. In such deposition systems the target needs to be powered with an electrical current such that a certain electrical potential is present on the target. There is therefore a need for termination units which are adapted for transferring power to the target they are carrying.
- Embodiments of the present invention relate to a termination unit for a deposition system.
- the termination unit comprises a device for effecting a function.
- the device comprises: at least one component comprising electrical steel, and at least one shielding element which is electrically conductive and which is configured such that if a neighboring current which has a first topology would be applied, an effect of the neighboring current on the component comprising electrical steel, which is not contributing to the function of the device, is mitigated by a current through the shielding element resulting in a counteracting field in the shielding element.
- the device moreover comprises a current transfer means neighboring the at least one component comprising electrical steel, wherein the current transfer means is adapted for guiding a current according to the first topology and for transferring power to a target when it is mounted on the termination unit.
- the current through the shielding element may be induced by the neighboring current. It is an advantage of embodiments of the present invention that an effect of a neighboring current, on the component comprising electrical steel, that is not contributing to the function of the device, is mitigated. This effect may for example result in energy losses in the component comprising electrical steel which are reduced by mitigating the effect.
- a more compact termination unit can be created which is suitable for rotating a target and for transferring electrical power to the target. It is thereby advantageous that the varying non-contributing magnetic field generated by the varying current to power the target is significantly reduced by the shielding winding.
- a single or a set of active currents may generate a time varying magnetic flux density that is higher than would be the case in air.
- Such devices may for example be found in electrical motors or transformers.
- an alternating external current (which may be a sine wave, a square wave, a pulsed wave or which may have any wave shape), not contributing to the operation of the device, is generating a magnetic field in the electrical steel, then this may lead to heating of the electrical steel caused by hysteresis losses and eddy currents.
- termination units are comprising means for reducing heating of the electrical steel which is induced if a varying magnetic field is present in the electrical steel which is not contributing to the operation of a device (e.g. motor or bearing) of the termination unit.
- the shielding winding is configured such that another neighboring current, which has a different topology than the first topology, can be applied for which the effect on the component comprising electrical steel is not significantly mitigated.
- At least one other current can be applied, which has a different topology and of which the effect is not significantly mitigated.
- selective mitigation of the effects is possible and for example only those effects may be mitigated which do not contribute to the operation of the device and/or which result in energy losses in the component comprising electrical steel.
- the shielding element is configured such that when a neighboring varying current would be applied which results in a varying non-contributing magnetic field through the electrical steel, which is not contributing to the function of the device, this neighboring varying non-contributing magnetic field results in a net magnetic flux through the shielding element, and this neighboring varying current results in a current through the at least one shielding element which results in a magnetic field which counteracts the non-contributing magnetic field.
- a potential non-contributing magnetic field generated by a potential neighboring varying current (e.g. through a neighboring current transfer means), through the electrical steel is smaller than would be the case when no shielding element is present.
- the neighboring current creates an EMF in the shielding element resulting in a current through the at least one shielding element which results in a magnetic field which counteracts the non-contributing magnetic field. This current counteracts and therefore reduces the non-contributing magnetic field.
- the non-contributing magnetic field may be generated by an external magnetizing current.
- a specific non- contributing magnetic field is reduced by the presence of the shielding winding. This is achieved by a shielding winding which is configured such that the varying non- contributing magnetic field results in a net magnetic flux through the shielding element. Other magnetic fields which do not result in a net magnetic flux through the shielding element will not be reduced.
- the at least one shielding element is a shielding winding which circumvents at least a part of the at least one component comprising electrical steel such that a(varying) non-contributing magnetic field, which is not contributing to the operation of the device, results in a net magnetic flux through shielding winding.
- the at least one component comprising electrical steel is adapted for guiding a contributing magnetic field contributing to the function of the device, wherein the at least one shielding element is positioned such that substantially no net magnetic flux through the shielding element originates from the contributing magnetic field.
- the operation of the device is not significantly or even not affected by the shielding element. This is achieved by arranging the at least one shielding element such that it does not substantially influence the contributing magnetic field.
- the shielding element is a shielding winding.
- the at least one shielding winding is positioned such that a surface of one winding is substantially orthogonal to a direction in which the magnetic field is contributing to the operation of the device.
- the shielding element is configured such that if a varying current is applied to the current transfer means this results in a current through the shielding element.
- the shielding element is designed to shield the effect of a varying current through a current transfer means having a specific topology. The shielding element is thereby designed such that at least some other topologies of neighboring currents can still induce a magnetic field in the component comprising electrical steel. It is an advantage of embodiments of the present invention that electrical power can be transferred to an external device without significant heating of the at least one component comprising the electrical steel.
- the transfer means for transferring power to an external device, crosses a circumference of the component comprising the electrical steel.
- the transfer means is adapted for transferring the current in a unipolar direction through the at least one component comprising electrical steel (no return path through the component).
- the transfer means is configured such that the transfer means crosses a circumference of the component comprising the electrical steel, and such that a return path of the transfer means is outside the at least one component comprising electrical steel.
- the transfer means is thereby configured such that, if an AC current is applied through the transfer means this implies that a unipolar AC current flows through the at least one component comprising electrical steel.
- the unipolar current will result in a magnetic field in the electrical steel. It is an advantage of embodiments of the present invention that this non-contributing magnetic field is compensated for by the shielding element.
- the component comprising electrical steel has a toroidal shape
- the at least one shielding element is a shielding winding which is substantially toroidally wound around the at least one component comprising electrical steel.
- the at least one shielding element is a shielding winding which is short-circuited.
- the at least one shielding element is a shielding winding is loaded by an impedance.
- the at least one shielding element is sunken and/or embedded in the at least one component comprising electrical steel.
- this may be a shielding winding. It is an advantage of embodiments of the previous claims that the at least one shielding element does not form a mechanical hindrance in the device and/or for the operation of the device.
- the at least one shielding element is positioned where the varying non-contributing magnetic fields are expected.
- the device is an electrical motor comprising a stator, and a rotor and wherein the stator and/or the rotor corresponds with the at least one component comprising electrical steel, and wherein the motor is configured such that a current can be applied to the motor resulting in the contributing magnetic field resulting in a torque force between the stator and the rotor such that the motor can rotate the target when mounted.
- the motor does not suffer significant torque losses by having the at least one shielding element present. Substantially the same torque is achieved with or without the at least one shielding element. The heating of the motor, however, is less with the at least one shielding element.
- the device is a bearing and the component comprising electrical steel corresponds with a ring of the bearing wherein the bearing is adapted for supporting the rotation of a mounted target.
- the transfer means comprises a central axis through the device.
- the central axis may for example be the rotor axis. It is an advantage of embodiments of the present invention that the non-contributing magnetic field in the stator and/or rotor of the motor caused by the alternating current through the central axis is reduced because of the at least one shielding element.
- Devices according to embodiments of the present invention may comprise a controller adapted for applying a DC current through the at least one shielding element to generate a non-contributing magnetic field.
- FIG. 1 and FIG. 2 show schematic drawings of a termination unit in accordance with embodiments of the present invention.
- FIG. 3 shows a schematic drawing of a motor with an external rotor in accordance with embodiments of the present invention.
- FIG.4 and FIG. 5 show the schematic drawing of a motor with an internal rotor in accordance with embodiments of the present invention.
- FIG.6 shows the cross section of electric steel with the presence of a current density through its internal perimeter.
- FIG.7 shows the influence on the effective motor torque due to the presence of an external DC current through the internal perimeter of a stator.
- FIG.8 shows the schematic drawing of a motor comprising a stator with a slit filled with air in the central part of the electrical steel.
- FIG. 9 shows the cross section of electric steel comprising a slit in the electrical steel.
- FIG. 10 shows an example of a stator cross section with open slits added in the material, in order to add magnetic reluctance that is situated in the major flux path of the magnetic field, not contributing to the useful operation of the motor.
- FIG. 11 shows the principle of a shielding wire that will counteract the induced magnetic field in the electrical steel, due to the presence of a potential external magnetizing current, in accordance with embodiments of the present invention.
- FIG. 12 shows the practical implementation of the shielding winding on the stator with slots provided at the inside of the stator and the shielding wiring returning over the stator winding in accordance with embodiments of the present invention.
- FIG. 13 shows the practical implementation of the shielding winding on the stator of a motor with slots provided in the electrical steel to house the shielding winding, in accordance with embodiments of the present invention.
- FIG. 14 shows a schematic drawing of a part of a stator comprising electrical steel wherein possible locations of shielding windings are indicated, in accordance with embodiments of the present invention.
- FIG. 15 shows the power loss in the stator comprising the power loss in the supply cable of the external current, when the shielding winding is open and when the shielding winding is closed, in accordance with embodiments of the present invention.
- FIG. 16 shows a curve wherein the electrical steel temperature is shown in function of time for a prior art device and for a device in accordance with embodiments of the present invention.
- FIG. 17 shows a schematic drawing of a bearing comprising one ring, in accordance with embodiments of the present invention.
- FIG. 18 shows a schematic drawing of a bearing comprising two rings, in accordance with embodiments of the present invention.
- a current which has a certain topology
- Such a carrier may for example go through the circumference of the component comprising the electrical steel.
- Embodiments of the present invention relate to a termination unit 300 for a deposition system.
- the termination unit comprises a device 100 for effecting a function, the device comprising at least one component 110 comprising electrical steel, and at least one shielding element 120 which is electrically conductive and which is configured such that, an effect of a neighboring current on the component 120 comprising electrical steel, which is not contributing to the function of the device, is mitigated, wherein this neighboring current has a first topology, and such that an effect of at least one neighboring current having a different topology than the first topology is not significantly mitigated.
- the device moreover comprising a current transfer means 140 neighboring the at least one component 110 comprising electrical steel, wherein the current transfer means is adapted for guiding a current according to the first topology and for transferring power to a target when it is mounted on the termination unit.
- a termination unit 300 connects a target 350, in a deposition system, with the outside of the deposition system.
- a termination unit 300 is typically mountable as a part of the deposition system.
- the pressure can be higher than in the deposition system. This pressure can for example be close to the atmospheric pressure. Parts which can be removed together with the target, or the removable magnet configuration, are typically not considered as part of the termination unit.
- the main function of the termination unit 300 is to carry the target and potentially also to rotate the target.
- Termination units are comprising a transfer means for transferring power to the target when it is mounted onto the termination unit. Thereby power may be transferred from the static part 360 of the termination unit to the rotating part 310 of the termination unit. In the example of FIG. 1 this is achieved through brushes 330.
- the central axis of the motor may for example be part of the transfer means and may be used for carrying the electrical current towards the target.
- the rotor 310 is used as part of the transfer means for carrying current to the target 350.
- the figure also shows a magnet configuration 324 on the rotor, a stator 320, a shielding winding 120 around the stator 320 and a housing 340.
- FIG. 2 shows a schematic drawing of the same termination unit as the termination unit in FIG. 1.
- the current transfer means 140 is indicated by the dashed line. It comprises the static part 360 of the termination unit, the brushes 330, and the rotating part 310 which is connected with the target 350.
- FIG. 2 also shows a wiring scheme for closing the current loop.
- the (unipolar) current transfer forms a closed circuitry around the component comprising electrical steel.
- the motor of the termination unit 300 comprises a shielding winding 120 which is configured such that an alternating non-contributing magnetic field, originating from an alternating current in the transfer means (e.g. the axis of the motor), results in a current through the shielding winding.
- the heating of the electrical steel in the rotor is reduced. This is especially the case when the current is transported through the motor axis 310.
- the same shielding element may be applied to the component 324, holding the magnet configuration of the rotor.
- the same losses and heating phenomena may apply to this part as well and the shielding element is an effective method of shielding the potential external current while the functionality of the rotor is not being affected substantially.
- Such a shielding element around the rotor of a motor is also illustrated in FIG. 5.
- the termination unit may for example be a PVD source termination unit. Since PVD deposition of a target can generate a lot of heat on the target surface, this surface needs to be cooled. This is typically achieved with water on any other suitable coolant.
- the termination unit may therefore comprise means for guiding the coolant and seals for sealing the cooling liquid.
- a termination unit 300 may comprise bearing means. These may for example support the target while it is turning around its axis. If the current towards the target 350 is carried by the axis of the motor, this current may also pass through the centre of the bearings and cause heating of the electrical steel of the bearings. It is in that case advantageous to these termination units are comprising bearings in accordance with embodiments of the present invention.
- the termination unit may moreover comprise means to position a magnet or a series of magnets in the target 350. These may be bearing means for supporting the magnet or series of magnets and/or driving means for generating a rotational movement.
- a termination unit also may comprise sealing means.
- a dynamic seal thereby typically comprises metal rings for sustaining the cylindrical shape of the seal.
- the termination unit comprises a current transfer means that carries a unipolar current through a component comprising electrical steel.
- the latter component is used for applying a rotational movement to the target (or to the magnetic bar) connected to the termination unit.
- This current transfer means is electrically isolated from the device 100 (e.g. from the motor, bearing or supporting structure) in order to enforce the current as a unipolar current through the component containing electrical steel.
- this unipolar current will act as a magnetizing current and generate a magnetic induction inside the electrical steel.
- This ring flux will not necessarily interfere with the magnetic topology of the functional behavior of the rotational component, but some major effects will result:
- this unipolar current can be significantly high and be one or two magnitudes larger than the active current in the rotational component. This may result in a magnetizing current that mostly saturates the magnetic steel.
- the frequency content of the unipolar current in a termination unit may for example be in the mid frequency range from 10 kHz up to 100kHz and may strongly differ from the frequency of the currents generating the contributing magnetic field. These currents may for example be in the frequency range from 5 to 100 Hz.
- the loss properties of the magnetic steel are optimized for the frequency range from 50 to 100Hz but are mostly unsuited for frequencies from 10kHz to 100 kHz.
- selecting electrical steel that is suited for frequencies from 10 to 100kHz is not possible as this kind of material does not exist or is extremely expensive.
- major magnetic losses will result inside the electrical steel, that will present major thermal problems in the termination unit.
- the shielding element e.g. shieling winding
- the active section of the shielding winding may be thicker than the thickness required for mitigating asymmetric magnetic fields created by stator asymmetries.
- the mid frequency range from 10kHz up to 100 kHz, might require the use of high frequency Litze wire, to lower the AC resistance of the wire. A reduced AC resistance will result in a reduced voltage drop over the shielding element (e.g. winding).
- the total voltage drop (product of induced current and the AC resistance) is preferably below 1.0V to limit the losses inside the electrical steel. This is advantageous because the resulting voltage drop will be in correspondence with a generated ring flux inside the electrical steel.
- a shielding element e.g. winding
- a low leakage flux is realized with a low leakage flux.
- the shielding element is configured such that when a neighboring varying current (having the first topology) would be applied which results in a varying non-contributing magnetic field through the electrical steel, which is not contributing to the function of the device, this varying non- contributing magnetic field results in a net magnetic flux through the shielding element, and this neighboring varying current results in a current through the at least one shielding element which counteracts the non-contributing magnetic field.
- the neighboring varying current may be carried by a neighboring current transfer means having the first topology.
- the shielding element is a shielding winding.
- the shielding winding can for example be a single wire (being of any shape), a woven cable, a non-woven cable or a Litze cable.
- the neighboring current transfer means may be next to the component comprising electrical steel or it may go through the component comprising electrical steel.
- Electrical steel thereby is an iron alloy. It may be tailored to produce specific magnetic properties such as a small hysteresis area resulting in low power loss per cycle.
- the electrical steel may comprise other materials like ferrites, laminations, and high permeability materials.
- the power loss may be caused by an alternating non-contributing magnetic flux density and is reduced by reducing this flux density compared to the situation wherein no shielding winding would be present.
- the non-contributing magnetic field may be generated by an external current not intended to contribute to the useful operation of the device.
- the current may for example flow over a current carrying conductor 140.
- the current carrying conductor may be in the neighborhood of the electrical steel component. This means it may be next to the electrical steel component or it may be surrounded by the electrical steel component.
- f is the frequency of the magnetic field variation and B is the magnetic flux density. This may be caused by an external current not contributing to the useful operation of the device.
- B is proportional to the current in the non-saturating working domain of the electrical steel, the losses will be proportional to the square of the current.
- the magnetic field is transferred from one side of the component comprising the electrical steel to the other side, creating the effect as if no electrical steel is present for the external current not intended to contribute to the useful operation of the device.
- the at least one component 110 comprising electrical steel is adapted for guiding a contributing magnetic field for operating the device 100. This may for example be the case for a transformer or a motor.
- the at least one shielding winding is positioned such that substantially no net integrated magnetic flux through the shielding winding originates from the contributing magnetic field.
- the potential presence of a non-contributing magnetic field has a flux path that is different from the contributing field.
- the at least one shielding winding may be short circuited or it may be loaded by an impedance.
- This may for example be a resistance, a capacitance, an inductance, or a combination of these elements.
- the device 100 is a motor.
- a motor may for example be a DC motor, an AC motor, a servo-motor, a stepper motor, a brushless DC motor, a reluctance motor, a torque motor.
- FIG. 3 A schematic drawing of such a motor with an external rotor 150, in accordance with embodiments of the present invention, is shown in FIG. 3.
- the figure shows the component 110 comprising electrical steel (which corresponds with the stator) and the at least one shielding wiring 120 which is toroidally wound around the stator.
- the shielding wiring 120 is wound between the teeth 130 of the stator.
- the motor windings 132 for operating the motor are wound around the teeth 130 of the stator.
- FIG. 3 also shows a central axis 140 which can be used as current transfer means for a potentially external current of another electrical circuit. This external current is not related in any way to a useful operation of the motor, but this current path is preferentially used because of geometric and technical reasons.
- the rotor 150 is only schematically drawn for indicating its position in the motor.
- the permanent magnets (when present in the motor) are for example not shown in this and the following figures.
- a similar embodiment can be found with the rotor 150 at the internal side of the stator 110 in FIG 2. Also in that case, a conductor 140 can be present inside the rotor that is used as a conducting means for a potentially external current. This conducting path could be as well the outside surface of the rotor.
- the rotor itself may be a component comprising electrical steel and a shielding element 120 may be configured such that a varying current through the neighboring current transfer means 140 results in a current through the shielding element 120 which results in a magnetic field which counteracts the non-contributing magnetic field. This is illustrated in FIG. 5 wherein the shielding element is a shielding winding 120 toroidally wound around the rotor 150.
- the potentially external current through the conductor 140 that acts as an unwanted magnetizing current for the electrical steel is of a kind that it is a unipolar current.
- otal Jfsurf ace internal J( . X, y)dxdy ⁇ 0.
- the current has a unipolar character.
- this total surface integral equals zero, then this is because an equal amount of current flows back inside the perimeter of the electrical steel. This is then in fact a two-conductor system with an entry and return conductor.
- the return current will be physically located outside the external perimeter of the electrical steel and mostly, outside the electromagnetic device that comprises the electrical steel.
- the line integral of the magnetic field over a closed curve inside the magnetic steel is related to the total current density of the potential external current that flows within the perimeter of the electrical steel internal surface
- B steel o r C ⁇ ) " H steel
- the created magnetic flux density B s teel is responsible for extra losses inside the electrical steel due to hysteresis losses and eddy current losses, as can be found in the datasheet of all ferromagnetic materials.
- the frequency content of the potential external current can be of such a kind that it is not favorable for the type of electrical steel used.
- the type of electrical steel is selected based on the working frequency and the level of the magnetic flux density in the air gap of the motor (situated between the stator teeth and the rotor electrical steel or permanent magnets when present on the rotor).
- the frequency content of the non-contributing field can be largely different from the frequency content of the flux density present for the torque generation in the motor. And this can be very unfavorable for the properties of the electrical steel.
- the magnetic flux density generated by a potential external unipolar current is of such a kind that in general, it will not transverse the air gap between the stator and the rotor structure. It will not directly interfere with the magnetic field, used for the motor operation. Indirectly however, it can add saturation to part of the stator steel, reducing the overall permeability 0 r of any practical magnetic steel and hence, this can influence the magnetic flux density generated by the stator windings and reduce the motor torque. Furthermore, due to the extra losses generated by the potential external current, the temperature of the electrical steel will rise and in general, this will reduce the magnetic permeability of the steel, resulting in a torque reduction of the motor for a given stator current.
- the potential (unipolar) external current can be a combination of a direct current (DC component) and an alternating component (AC component), showing a magnitude on the spectral content, linked to the nature of the application of the external circuit.
- the DC component of the potential external current will not create hysteresis and eddy current losses inside the electrical steel of the motor, as the frequency of the created magnetic flux density equals zero Hertz. Indirectly, it will create a magnetic field H inside the electrical steel, that will superimpose on the magnetic field created by the stator winding inside said magnetic structure.
- the thickness of the shielding conductor inside the added airgap should be at least several times the skin thickness for the given frequency content of the potential external current (FIG.8, e.g. slit filled with an isolated solid copper conductor).
- Adding magnetic reluctance inside the continuous core of the stator is an effective means in reducing the flux density generated by a potential unipolar external current, traversing the internal perimeter of the electrical steel. This can be seen from the equations that result when adding an airgap in the flux path inside electrical steel.
- Magnetic reluctance can be added into the electrical steel of a stator by introducing at least one 'airgap' or slit (filled with a non-magnetic material that can be conducting, but should be isolated from the electrical steel if the latter is conducting).
- a complete cut-out in the core of the electrical steel (FIG.8), can jeopardize the mechanical stiffness of the stator, partly slits can be made to create the same effect (FIG.10).
- electrical steel consists of a stacked lamination assembly, it can be stacked in such a way that slit is located for many laminations at the same position, and then subsequent stacking can rotate the slit location to another location. This process can be done several times. When everything is fixed together, some substantial mechanical stiffness will result.
- the thickness of the shielding material should be at least three times the skin depth of the surface currents, as determined by the frequency content of the potential external alternating current. In that situation, no alternating magnetic field will be found at the inside of the closed shielding, hence no losses will be present in the electrical steel.
- the potential external current can pass through the shielded electrical steel as a unipolar current. In that case, a donut based hole must be provided in the shielding, so that the conductor with a unipolar current can pass through the shielding, the latter still forming a closed structure.
- the external return current is found in a conductor outside the shielded structure.
- the contributing magnetic field of the motor which is of an alternating nature, should not be mitigated by the enveloping Faraday shield.
- the magnetic field between the stator and the rotor can therefore not penetrate the shielding structure. This means that the shielding should surround both the stator and the rotor structure, so that no integrated change of flux by the contributing field can be found over the surface of the shield.
- the mechanical power generated by the rotor of the motor should be transferred outside of the enveloping shield. This can only be realized by providing a mechanical feed-through in the shielding structure, giving a discontinuity in the electrical conduction on the shielding surface. In most cases, this will give a major loss of shielding effectiveness.
- the problem can be solved by providing a moving part in the shield that has a continuous electrical connection with the fixed part of the shield, e.g. by implementing the use of brushes or sliding contact parts.
- a Faraday shielding is also very universal: it will shield the presence of every external current from the electrical steel at the inside of the shielding structure. In practice, the shielding is preferably only effective for a specific topology of the conductors carrying the potential external non- contributing current.
- the shielding element is configured such that it only counteracts the non-contributing magnetic field, but does not affect the contributing magnetic field of the motor. In this way, the shielding element can be confined to a fixed part on the stator and on the rotor only, removing the problem of the mechanical feed-through in the Faraday shielding.
- the device is a motor and the current transfer means is a conductor along the central axis of the motor which is adapted for carrying a current for powering an external device.
- the varying (e.g. alternating) part of this current has the properties that it will create unwanted excessive magnetic losses (hysteresis losses and eddy current losses) inside the electrical steel.
- the at least one shielding element e.g. winding
- the at least one shielding element is applied such that it does not counter-act the magnetic field of the normal motor operation (hence the motor windings do not induce voltages in this at least one shielding winding), but opposes the field created by the central axial current component.
- the at least one shielding winding is short-circuited, so that by definition, no magnetic field can be built-up for the flux density created by the potential external current. In practice, this alternating non-contributing magnetic field is strongly reduced because of the presence of the at least one shielding winding, and this results in a major drop of the magnetic losses inside the electrical steel as this is proportional to the square of the magnetic flux density.
- Hsteei will not become zero, as a voltage drop is present over the shielding winding. This voltage drop will present itself as some valued magnetic flux density that will be present in the electrical steel, created in the end by the potential external current.
- the shielding current l s has therefore also the same alternating nature and the skin effect might be present in the winding material, increasing the effective resistance of the shielding wire, as the current flow is confined to the circumference of the solid wire part.
- the skin effect is extensively described in literature and technical reports. When the shielding wire consists of several wires, then the proximity effect will be present as well.
- the shielding wire current l s will in practice also create a magnetic flux density in parts of the air around the physical location of the shielding wire. This means that some inductive energy is stored in the winding that is not linked to flux density in the iron steel. This is well known in literature as leakage flux. Due to the alternating nature of the current in the shielding winding, a voltage drop will result due to the presence of this leakage flux.
- At least one shielding wire can be loaded by an electrical impedance.
- This is a parallel or series combination of capacitors, inductors, resistors.
- the effect of leakage inductance of the shielding wire can be compensated by adding a series capacitor in the shielding winding, which is tuned to the working frequency of the potential external current. This will lower the voltage drop over the shielding wire and hence, lower the losses generated by the external current.
- the type of shielding winding may be selected based on the frequency content of the potential external current that will be applied. For very low frequencies, a solid thick wire can be used, having a very low ohmic resistance. For mid and high frequency ranges, a braided wire or Litze wire can be used, having a large surface area, being little influenced by the skin effect.
- the winding is applied such that it counteracts the potential external magnetizing current (e.g. through a central conductor) by using a kind of toroidal winding around the core.
- a "kind of” hereby refers to the fact that the winding may be adjusted from its toroidal shape so that it fits in a certain position of the component comprising electrical steel. It may for example be positioned between the teeth of a stator.
- FIG. 12 shows the component 110 comprising electrical steel, which in this example is a stator, the slots 134 with therein the stator windings 132, and the shielding winding 120.
- extra slots 135 can be provided at the inside the stator (FIG.12 and FIG. 13).
- a further reduction of the leakage flux can be achieved by providing an extra slot 136 at the outside of the stator, beneath the winding slots 134 (FIG. 13).
- extra slots in the stator will diminish the effective magnetic area of the electric steel, but it can give manufacturing benefits as the shielding winding is located at well-defined position.
- holes can be used as well.
- FIG. 14 is a schematic drawing of a part of a stator comprising electrical steel wherein possible locations of shielding windings are indicated.
- the slots are indicated by references 1, 2, 3, 4.
- a cross-winding is made where the shielding winding of slot 1 and slot 2 are connected together.
- a shielding winding may extend to 3 or 4 or more slots.
- the position (comprising the number of windings of the shielding winding) can be determined based on the current pattern for operating the motor in order to prevent an interaction with the motor current. Thereby the shielding winding should be positioned such that substantially no net magnetic flux through the shielding winding originates from the contributing magnetic field.
- a toroidal winding may comprise a plurality of windings enclosing 2 or more, or even all slots of the stator.
- the sum of the current in all slots being covered by the shielding winding equals zero, substantially no net flux will be generated in the shielding. Hence, the motor operation will not be influenced by the presence of the shielding winding.
- Ampere windings results in zero amps, then the shielding winding can be locally applied to cover these slots. The same approach can be followed for the remaining stator slots. So, this means that a single toroidal winding can always be replaced by a set of individual toroidal windings, that cover a limited segment of the stator. But each of these shielding windings needs to be a closed loop.
- the wires are shorted or a load impedance is added (in order to enhance the behaviour of the shielding wire).
- it is easier to use a single shielding wire as the return conductor between the start and the end of the shielding winding will be relatively short.
- the effect of the shielding winding is not limited to reducing the magnetic losses in the electrical steel as such. Moreover, almost no energy will be stored in the electrical steel due to a field not contributing to the motor operation of the device. Due to the shorted shielding winding, the stator flux generated by the potential external alternating current will be small (in accordance with the voltage drop over the shielding winding, which is kept small by design). So, this results in a low magnetic energy storage and the physical effect seen by the circuit that contains the external electrical current is that the leakage induction will be small. When dealing with varying (e.g. alternating) currents, this means that the voltage drop over the conductor, passing through the perimeter of the electrical steel, will also remain small.
- this shielding winding can also be used for shielding the effect of the presence of a potential external DC current.
- Idc external DC current
- Devices according to embodiments of the present invention may comprise a controller for generating such a current.
- FIG. 15 shows the losses in the stator when the shielding wire is active (210) and not active (220) (by simply opening the shielding wire circuit).
- the input current goes in the range from 5 to 160A and did have a frequency of 40kHz. As can be seen the losses are significantly decreased when the shielding wire is active.
- FIG. 16 shows a curve wherein the electrical steel temperature is shown in function of time. The curve is obtained when applying an alternating axial current of 150 A. In the first half hour the shielding winding was open showing a steep increase of the electrical steel temperature.
- the device is a bearing and the component comprising electrical steel corresponds with a ring of the bearing.
- FIG. 17 shows a bearing with one ring wherein the ring corresponds with the component 110 comprising electrical steel.
- the shielding winding 120 is toroidally wound around the ring.
- the shielding winding is sunken in the ring such that it cannot hinder the rotation of the ring.
- FIG. 18 a bearing is shown with two concentric rings 110 wherein a shielding winding 120 is toroidally wound around each of the rings. Each winding is mounted sunken into its corresponding ring.
- the bearing may be chosen to be appropriate for the specific application and may of any type known; such as but not limited to ball bearings, roller bearings, plain bearings, axial bearings or any type known in the art.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Analytical Chemistry (AREA)
- Plasma & Fusion (AREA)
- Electromagnetism (AREA)
- Power Engineering (AREA)
- Motor Or Generator Frames (AREA)
- Iron Core Of Rotating Electric Machines (AREA)
- Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
- Coupling Device And Connection With Printed Circuit (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
- Input Circuits Of Receivers And Coupling Of Receivers And Audio Equipment (AREA)
- Physical Vapour Deposition (AREA)
Abstract
Description
Claims
Priority Applications (6)
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KR1020207015299A KR102517088B1 (en) | 2017-11-01 | 2018-10-15 | termination unit |
RU2020117421A RU2020117421A (en) | 2017-11-01 | 2018-10-15 | END BLOCK |
JP2020543700A JP7218377B2 (en) | 2017-11-01 | 2018-10-15 | termination unit |
CN201880070999.3A CN111295824B (en) | 2017-11-01 | 2018-10-15 | capping unit |
EP18783049.2A EP3704786A1 (en) | 2017-11-01 | 2018-10-15 | Termination unit |
US16/759,869 US11365474B2 (en) | 2017-11-01 | 2018-10-15 | Termination unit |
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EP (1) | EP3704786A1 (en) |
JP (1) | JP7218377B2 (en) |
KR (1) | KR102517088B1 (en) |
CN (1) | CN111295824B (en) |
RU (1) | RU2020117421A (en) |
TW (1) | TWI818927B (en) |
WO (1) | WO2019086236A1 (en) |
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EP3193432A1 (en) * | 2016-01-15 | 2017-07-19 | Toyota Jidosha Kabushiki Kaisha | Stator and electric motor |
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CN1195918A (en) * | 1997-04-10 | 1998-10-14 | 袁训中 | Acyclic dc electric machine |
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EP1540631B1 (en) * | 2002-08-29 | 2012-02-08 | William W. French | Fluid suspended self-rotating body and method |
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JP5469873B2 (en) * | 2008-03-11 | 2014-04-16 | 株式会社日立製作所 | Rotating electric machine |
SG172815A1 (en) * | 2009-01-12 | 2011-08-29 | Redemptive Technologies Ltd | Decreased drag high efficiency electric generator |
CN103748642B (en) * | 2011-06-01 | 2017-08-25 | Analogic公司 | Power coupling device with shielding |
US9130433B2 (en) * | 2013-11-14 | 2015-09-08 | Arm Limited | Electronically controlled universal motor |
WO2016180444A1 (en) | 2015-05-08 | 2016-11-17 | Applied Materials, Inc. | Radio frequency (rf) - sputter deposition source, connector for retrofitting a sputter deposition source, apparatus and method of operating thereof |
KR101638294B1 (en) * | 2015-10-27 | 2016-07-08 | (주)항남 | Apparatus for Manufacturing Laminated Core by Heating Adhesion |
JP2018061392A (en) * | 2016-10-07 | 2018-04-12 | 株式会社デンソー | Armature and rotary electric machine |
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2018
- 2018-10-15 KR KR1020207015299A patent/KR102517088B1/en active IP Right Grant
- 2018-10-15 CN CN201880070999.3A patent/CN111295824B/en active Active
- 2018-10-15 EP EP18783049.2A patent/EP3704786A1/en active Pending
- 2018-10-15 JP JP2020543700A patent/JP7218377B2/en active Active
- 2018-10-15 RU RU2020117421A patent/RU2020117421A/en unknown
- 2018-10-15 US US16/759,869 patent/US11365474B2/en active Active
- 2018-10-15 WO PCT/EP2018/078124 patent/WO2019086236A1/en unknown
- 2018-10-24 TW TW107137458A patent/TWI818927B/en active
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DE1613065A1 (en) * | 1967-11-27 | 1970-12-03 | Schorch Gmbh | Damper winding for magnetic ring fluxes in the laminated core back of rotating electrical machines |
US20050121992A1 (en) * | 2003-12-05 | 2005-06-09 | Siemens Westinghouse Power Corporation | Counteracting magnetic field generator for undesired axial magnetic field component of a power generator stator and associated methods |
WO2011029647A2 (en) * | 2009-09-08 | 2011-03-17 | Robert Bosch Gmbh | Synchronous machine |
US20120086288A1 (en) * | 2010-10-08 | 2012-04-12 | Denso Corporation | Electric rotating machine |
DE102013106168A1 (en) * | 2013-06-13 | 2014-12-18 | Von Ardenne Gmbh | Cantilever magnetron with a rotating target |
EP3193432A1 (en) * | 2016-01-15 | 2017-07-19 | Toyota Jidosha Kabushiki Kaisha | Stator and electric motor |
Also Published As
Publication number | Publication date |
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EP3704786A1 (en) | 2020-09-09 |
RU2020117421A (en) | 2021-12-01 |
TW201933735A (en) | 2019-08-16 |
JP7218377B2 (en) | 2023-02-06 |
US11365474B2 (en) | 2022-06-21 |
CN111295824B (en) | 2023-09-15 |
KR102517088B1 (en) | 2023-04-04 |
US20200287445A1 (en) | 2020-09-10 |
JP2021501269A (en) | 2021-01-14 |
CN111295824A (en) | 2020-06-16 |
KR20200084001A (en) | 2020-07-09 |
TWI818927B (en) | 2023-10-21 |
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